Known concealed spaces and fire protection systems are shown in Tyco Fire Protection Products' publication, TFP632: “Model CC2—4.2 and 5.6 K-Factor Combustible Concealed Space Sprinklers Specific Application, Upright” (March 2014) (hereinafter “TFP632”). The concealed space is defined as the space between an upper deck and a ceiling deck, which separates the concealed space from an adjacent area below the ceiling deck. As shown in TFP632, the construction of the concealed space can employ spaced apart truss or bar joist members that extend from the upper deck to the ceiling deck (FIGS. 2, 4 and 7 of TFP632) with a top chord engaged with the upper deck and a bottom chord engaged with the ceiling deck thereby interconnecting the upper and ceiling decks. The top chord extends from the upper deck into the concealed space and terminates at a bottom surface of the top chord. The bottom chord extends from the ceiling deck into the concealed space and terminates at a top surface of the bottom chord. The concealed space can be alternatively constructed with joist members (FIGS. 3, 5 and 6 of TFP632) spaced along the upper deck and separate joist members spaced along the ceiling deck. The upper deck joist members extend from the upper deck into the concealed space and terminate at a bottom surface of the upper deck joist members. The ceiling deck joist members extend from the ceiling deck into the concealed space and terminates at a top surface of the ceiling joist members.
Fire protection systems for concealed spaces employ automatic sprinklers located about the concealed space to address a fire. Known concealed space automatic sprinklers include a frame body having an inlet for receipt of the firefighting fluid, an outlet with a passageway extending between the inlet and the outlet to define a discharge coefficient of a nominal K-Factor of either 4.2 gpm/psi1/2 or 5.6 gpm/psi1/2. These known automatic sprinklers include a seal assembly supported in the outlet for a controlled release by a thermally responsive trigger. The triggers of known concealed space sprinklers are embodied as thermally responsive glass bulbs. The known trigger and frame body assembly provide for a sprinkler thermal response which can be characterized as “fast response,” as is understood in the art. Moreover, the thermal responsiveness of the known concealed space automatic sprinklers can be characterized by a response time index (RTI) of 32 (m-s)½ and a temperature rating of 175° F. These known combustible concealed space sprinklers include a deflector for the distribution of the firefighting fluid. The deflector is a generally planar member with a central portion axially aligned with the passageway and an outer peripheral portion circumscribed about the central portion to define a substantially circular periphery and a diameter of 1 11/16 inches. The peripheral portion of the deflector includes radially spaced apart tines to define a plurality of open ended slots formed therebetween extending radially inward at an equal distance toward the center of the member. The frame body includes a pair of frame arms diametrically opposed about the outlet to support the deflector spaced from the outlet. The deflector defines the sprinkler-to-sprinkler spacing and maximum coverage areas of the sprinkler. For the known sprinklers, the sprinkler-to-sprinkler spacing ranges from a minimum of seven feet to a maximum of twelve feet with a maximum coverage area of 144 square feet.
The installation, design and performance of these known fire protection systems are limited by the effective depth over which the fire protection system can address a fire. The “effective depth” is defined as the vertical space or distance over which the sprinkler(s) provide fire protection. The effective depth of the sprinkler and its installed position within the concealed space can define an “effective depth range,” which is the actual distance over which fire protection is provided within a concealed space as measured between either: (i) the upper and ceiling decks or (ii) between the top and bottom surfaces of opposed chords or joists disposed along the upper and ceiling decks.
Under current industry accepted installation standards such as for example, NFPA 13: Standard for the Installation of Automatic Sprinkler Systems (2013 ed.) (“NFPA 13”), the effective depth range for concealed space fire protection sprinklers is limited. Under Section 8.15.1 of NFPA 13, the installation of fire protection sprinklers for combustible concealed spaces is limited to use where the distance between either: (i) the upper deck and the ceiling deck; or (ii) in the case of joist construction, the distance between the top surface of the bottom joist and the bottom surface of the upper joist is no more than thirty-six inches (36 in.) and the sprinkler is “listed” for such use. Accordingly, the current effective depth range for which concealed space fire protection can be provided using sprinklers is limited to no more than thirty-six inches (36 in.). Under NFPA 13, to be “listed” means that the sprinkler is appropriately published stating that the sprinkler meets appropriate designated standards or has been tested and found suitable for a specified purpose.
For known concealed space fire protection systems, such as those shown in TFP632, the location of the measured maximum thirty-six inch effective depth range limitation is determined at least in part by the construction of the concealed space. For example, truss or bar joist constructions in which the top chord has a vertical length of 4 inches or less, the effective depth range is measured between the upper and ceiling decks. For joist constructions or for truss/bar joist constructions with top chords of greater than 4 inches in vertical length, the effective depth range is measured between the opposed bottom and top surfaces of the respective upper and ceiling joist or chord members.
The automatic sprinklers of known fire protection systems for combustible concealed spaces are upright sprinklers coupled to a supply pipe of firefighting fluid and located within the effective depth range. Thus for example, where the effective depth range has an upper boundary defined by the upper deck, a vertical axis extending from an installed sprinkler first intersects a perpendicular plane that includes the upper deck. The lower boundary of the effective depth range would be the opposed surface at the ceiling deck in a perpendicular plane intersecting the vertical axis extending from the sprinkler. Where the effective depth range has an upper boundary defined by the bottom surface of an upper chord or joist member along the upper deck, a vertical axis extending from the installed sprinkler first intersects a perpendicular plane that includes the bottom surface of the chord or joist member. The lower boundary of the effective depth range would be the opposed top surface of the bottom chord or joist along the ceiling deck in a plane perpendicular to the vertical.
The size of the concealed space itself can be limited because of the maximum thirty-six inch (36 in.) limit for the installation of combustible concealed space fire protection systems. For example, in a first known concealed space configuration with sprinkler protection in which the fluid supply pipe is CPVC pipe and the upper deck defines a slope relative to the ceiling deck that does not exceed 2:12 with one of unobstructed wood truss construction and combustible bar joist construction, the distance between the upper deck and the ceiling deck is limited to a range between a minimum of twelve inches to a maximum of thirty-six inches (12 in.-36 in.). In a second known protected concealed space configuration wherein the fluid supply pipe is CPVC pipe and the upper deck defines a slope relative to the ceiling deck that does not exceed 2:12 with one of non-combustible insulation-filled solid wood or composite wood joist construction, the distance between the joist members is limited to a range between a minimum of six inches to a maximum of thirty-six inches (6 in.-36 in.). In a third known protected concealed space configuration wherein the fluid supply pipe is steel pipe and the upper deck defines a slope relative to the ceiling deck that does not exceed 2:12 with one of unobstructed wood truss construction and unobstructed bar joist construction, the distance between the upper deck and the ceiling deck is limited to a range between a minimum of twelve inches to a maximum of thirty-six inches (12 in.-36 in.).
In three additional alternative known protected concealed space configurations wherein the fluid supply pipe is steel pipe and the upper deck defines a slope relative to the ceiling deck that does not exceed 2:12, with the upper and ceiling decks being any one of (i) solid wood joist construction; (ii) non-combustible insulation-filled solid wood or composite wood joist construction; or (iii) obstructed wood truss construction, i.e. top chord of greater than 4 inches in depth, the distance between the respective joist or chord members is limited to a range between a minimum of six inches to a maximum of thirty-six inches (36 in.).
It is believed that there is a desire to provide fire protection for concealed spaces with greater depths or spacings. By increasing the effective depth range of the fire protection systems, concealed spaces of sizes greater than currently known may be realized.